Sealed secondary batteries, such as lithium-ion batteries, have become widely used for portable electronic apparatuses and the like. The sealed secondary batteries each comprise a battery cell, which comprises, for example, an open-topped metal container and a metal cell cap welded to the container so as to close its opening. Battery elements are located in the container before the cell cap is welded to the container, and thereafter, the cell cap is welded to the container to form the sealed battery cell. Then, an electrolyte is injected through an electrolyte injection hole into the battery cell by an electrolyte injection nozzle. After the electrolyte is thus injected, the injection hole is sealed with a seal lid.
A well-known secondary battery manufacturing device comprises an elastic electrolyte injection nozzle, vacuum pressure source, on-off valve, and electrolyte supply device. In this manufacturing device, the electrolyte injection nozzle is first brought into contact with the electrolyte injection hole, thereby sealing the injection hole from the outside. Then, the valve between the nozzle and vacuum pressure source is opened to decompress the cell. The valve is closed in a predetermined time or when vacuum pressure is reached. Further, the electrolyte supply device is actuated to inject a predetermined amount of electrolyte into the cell through the nozzle.
In a method using a hopper disposed on the top of an electrolyte injection nozzle, on the other hand, the hopper is placed on the cell so that the nozzle abuts the injection hole. If a necessary amount of electrolyte is injected into the hopper and introduced into a decompression chamber for pressure reduction, the cell is decompressed by means of the electrolyte. If the chamber is restored to atmospheric pressure, thereafter, the electrolyte in the hopper is urged to be injected into the cell by atmospheric pressure.